24 WEST, ON PETALS OF FLOWERS. 
representation of part of the petal of the scarlet geranium, 
under a very low power. That the radiating lines seen not 
unfrequently on the cell-wall in this situation can have any 
appreciable effect in producing the brilliancy of flowers, as 
maintained by Schleiden, seems, however, more than 
doubtful. 
These papillz, or “ mammiliform protuberances,” may be 
either marked with lines or dots, or smooth and destitute of 
both. Good examples of these lines are presented by the 
petals of geranium (fig. 5), and pelargonium (fig. 14). 
When the outer cell-wall is papillate, they assume a radiate 
arrangement, which is seldom distinctly perceptible in the 
cells of petals, the surface of which is pla. These lines 
have been considered by Schleiden and Carpenter to be 
probably due to secondary deposit, and such was, up to a 
recent period, my own belief. In examining the petal of 
ladies’ bedstraw (Galiwm verum, fig. 10), [found an interesting 
condition of the parts. The cells here are not elevated above 
the general surface into papille, but are covered with large, 
raised, tubercle-like spots, arranged with considerable regu- 
larity, of a glassy transparency, and showing section dis- 
tinctly. Some idea of their appearance may be formed by 
imagining a plate of glass, whilst still soft, to be pressed out 
in spots by a small blunt tool, and cooling rapidly, to retain 
the impressions thus caused, which, by turning the glass over, 
would become elevations on the now uppermost surface. 
Similar tuberculoid dots are found on the lobelia before- 
mentioned on Antirrhinum majus, &c.  Schleiden long 
ago described “ tubercles”’ studding hairs from the fornix of 
Anchusa Italica, and figures them as if formed by layers of 
successive deposit m some cases. In this he has been 
followed by other authors; and Quekett represents some of 
them detached, as if rubbed off, which, were they really 
tubercles, might occur. At the time when this Anchusa was 
in flower, I was unfortunately too much engaged to be able 
to hunt after it; but hairs presenting external “elevations are 
not uncommon. 
The example of Galium just mentioned showed con- 
clusively, however, that tubercle-like elevations might be 

ee oe aa aS ee 
Fig. 3 Fig. 4. 
present on the walls of cells, or their prolongations, without 
the presence of external secondary deposit. The cell-wall is 
pretty thick, firm, of exquisite transparency, and can be 
